The present invention relates to an improved method for removing hydrogen sulfide from gases. More specifically, the present invention relates to a method for removing hydrogen sulfide from fuel gases by scrubbing with organic solvents.
Produced fuel gases such as natural gas and petroleum like gas fractions often contain substantial concentrations of hydrogen sulfide. Normally, hydrogen sulfide must be removed before the produced gas is suitable for sale or distribution through pipelines, in order to meet the product specifications required by commercial gas suppliers. It is also desirable to remove hydrogen sulfide from fuel gases before they are burned to reduce sulfur oxides emissions. In addition to produced fuel gases, other gases such as petroleum refinery offgas streams, are often contaminated with hydrogen sulfide. The presence of hydrogen sulfide can be detrimental and such gases are used in hydrocarbon or petrochemical processing. The presence of hydrogen sulfide also complicates the disposal of refinery gases by, for example, flaring, since sulfur dioxide produced during burning poses an emissions problem.
Various techniques have been suggested for removing hydrogen sulfide from fuel and other gases.
Among the methods proposed for removal of hydrogen sulfide from gases has been the use of solid, dry material such as zeolites or iron sponge. The use and regeneration of zeolites is often impractical for processing large quantities of relatively inexpensive natural gas. Another technique for removing hydrogen sulfide from gases has been scrubbing gases with aqueous or other liquid solutions. Generally, liquid materials such as aqueous solutions of amine, alkanolamines, potassium carbonate and the like, which have been used to remove hydrogen sulfide from gases by liquid phase scrubbing also removes substantial amounts of carbon dioxide and keep the gas streams saturated in water vapor. As aqueous and other liquid scrubbing processes usually operate by forming a chemical addition produce of hydrogen sulfide and, for example, an amine in liquid solution and then stripping the hydrogen sulfide out of the liquid solution in concentrated form. Disposal of this concentrated hydrogen sulfide usually requires a Claus unit or the like for converting hydrogen sulfide to sulfur.
Other methods of removing hydrogen sulfide from gases include contacting the gases with iron oxide. Iron oxide has been used in the form of pellets, powder and the like and has been used on essentially inert solids supports such as wood shavings, clays and the like. One problem with solid beds such as iron oxides sponges is that removal of the spent iron oxide sponge tends to be difficult. The hyrogen sulfide tends to bind the mass into a cohesive solid unit resistant to convenient removal means such as water spraying.
Another component frequently present in fuel gases is water. It is desirable to remove water from fuel gases since water vapor in gas streams can cause condensation and corrosion problems in pipelines. Conventionally, water is removed from a wet gas in a separate step by contacting the gas with a hydroscopic liquid, for example, diethylene glycol.